Hot top and element for producing the same



' Cross Reference Feb. 3, 1942. A. NICHOLAS 2,272,018

HOT TOP AND ELEMENT FOR PRODUCING THE SAME Filed Jime so, 1939 2Sheets-Sheet 2 Bnventor (Ittornegs Examiner Patented Feb. 3, 1942 norTOP mnnmnmn'rroa rnonccmo m SAME Isaackflicho'lasalittsblrgh;Pa.,-lssignor-to-The 'Standard Lime and StoneCompany, Baltnnore, eMd a corporation of Maryland kmilication'ilune 30,1939, Serial No. 282,259

4; Claims. 22-447) This inventionjpe'rtainsto hot tops, which-arecommonly employed in conjunction with ingot molds .to facilitatethefllling thereof andtoprefvent piping "and the formation of otherdefects in the ingot. .Itis particularly: applicable to hot 'Ttopsforingot molds inthe manufacture of steel.

The hottop of the present invention presents -inany advantages over theusual ihot top now 'commonlyemployed-and some ofthese advan- 'tages maybe stated generally asfollows: light- 'ness of structure, "together.with compactness in storage; easeofplacement with reference to theingot :mold; beneficial effects of the residue of the hot .topelements'with reference to the .mill scale formed as "the .result ofrolling .the .ingot, along with the production of a hi'ghgrade ingotsubstantiallylfree of "hanger tracks :and other surface andinterior.de'fects .such as'voids which are often present under presentday ,practice;

and the maintenance of fluidity of the upper portion of the ingot withthe result that acids and piping, as well as croppage, are held 104;Other advantages will hereinafter appear.

tend to freeze to theiirebflck'in this mold to the same degree as in thehollow ="flre clay inolds. As theingot shrinks, due tothetapering'shapeof the hot topfit tends to=pu1l away from'the brick. "-Yet evenin 'thisstyle of'hot top, some Elli-e brick adheres t and contaminates thesteel. "Offsetting this advantage of shrinkage is the :complexity or the'hot top itself and its greater lmnnbersomeness and weight as comparedto a 'clay hot top. Moreover, a rim 01 baked fire clay must :be .placedabout the bottom of the steel easing to make ra tight joint between "thecasing and mold. mgain, ithe lire 'bzick'ilning I lot the steel casingsmust be frequently u'enewed.

"Fire clay -mainly is used at the presenttime in the manufacture ofrhotrtopselther'usedalone or mixed with a number-0f substances such asehnmotte, woke, rhinestone, shale, 'etc; The hot top ingredients aremixed with :sumc'ient water to iorama plastic mass which is molded tothe desired shapeand then fixed -ina-kiln. The (resulting product sishard and ordinarily has a crushingstrength lot the ordenof'opflo to15,000 lbs.--per square inch; .Upto therpresent time, -it

Most nottcpsi'nizusetedayare'rormeo in whole has been aqnsiderednecessary-that t D or ln partoflflre-clay molded tothe desired shape andinen burned :or fired. :Such hot 'tops are heavy and necessitatemechanical equipment and thepresence of atlleast ltwo -men vtofacilitate the mold. IMoreover,-when sudh hot top is stripped or brckenaway 1mm the ingot, portions of *the burned claywill-adhere thereto to agreater'or less extent .due to the metal of the ingot freezmg to thetire clay. Here, again, manual labor with'itsattendantexpensels'esse'ritial.

Moreover, lt'isimpossibleto remove all of th adherent fire -clay froman'ingot, so that such adherent portions 'of'the burned clay are carriedbyithe ingot .into ithe'iblooming'mill where they have a-iieleteriousbiiect *upon the ingot and likewise 'cause roll "trouble andcontamination of thexolrsealamakingthecscale objectionable lor usetin anopen hearth or-"a blast ifurnace charge. on the other 'hand, thematerial, or materials, employedrtoproduce the hottopof the presentinvention have a benelicial eflect when *used in connection "with suchcharges.

'I'he disadvantages or the hollow fire clay hot top are overcome in partby the use-of-a hot top consisting or astelcasing-lihed withfire'bricks,

which tapers gently upwardand which'isfpla'ced in the top oi'the'ing0tmold imthes'ame manner.

After the ingot has -solidified,' this 'typepf '-=hot top can be lifted'ofi the-mold. The-steel does-not should retain greatstrength athightemperature, as Jsthe oase with i fine relay, in order to withstand the'pressure .ofrthermolten steel. I have I {diseoveredithat this is.notnecessaryvand that a placement thereof with reference to the ingot 0hcatonneed-nothave ssreater'cmshine s e than 10 $0 .15 lbs. .-per squareinch, and may have evenless. This 'is explained by the fact that moltenmetal solidifies instantly .when -it touches a,,relative1y.coldlsubstance. Thus, in pouringmolten metal in a button .ofwanycomposition, the 'skin' of solid steel whichimmediate- 1y forms entiresurface otthe hottop increases in thickness. ring or layer of solidsteel has sumcient strength to hold within itself a considerable head oimoltenmelt and requires little support trom'the hot top itself. Thisdiscovery has enabled me to produce a hot top composed essentlally ofbasic .materials. While .the new hot top oi my invention haspracticallylittle strength andwill "decompose at high temperatures, nevertheless ithas 'proven to be very satisfactory in actual steel pouring operationsand to possess .a number 01' decided advantages over a fire clay-bearingmaterial. The'preferred basic materials arefmagnesiuman'd calciumcarbonate, either "artificially prepared nr occurring in the naturalstate, and'also dolomite.

when'molten steel comes in contact with such a not top, the carbonateswill partially decompose. "Carbon'dioxide gas is driven omleaving apowder of magnesium and calcium oxides which have excellent insulatingproperties. on stripping, most of the hot top material does not stick oradhere to the ingot and the portion remaining on the ingot is readilyremoved when it comes in contact with the blooming mill rolls. Fire clayhot tops become imbedded in the ingot and the greater portion is notremoved upon stripping. When the ingot is rolled, the fire brick isbroken away together with the scale which coats the ingot. Ingot scale,or so-called roll scale, is a valuable by-product in steel making. It isa very pure form of iron oxide and is used in blast furnace and openhearth operations. When it is contaminated with fire brick it becomesalmost useless, as fire brick is very refractory and is dissolved withgreat diificulty in a blast furnace or open hearth slag. One of theadvantages of this invention is that roll scale if contaminated with thebasic materials from which the hot top is made, is improved in itssmelting properties.

The excellent insulating property of the basic hot top of this inventionis another important advantage. The superiority of magnesia over fireclay brick is well known. The insulating effect of the MgO formed whenthe hot top decomposes is reflected in an increased yield of soundbillets. During a direct test made in a large steel plant extending overa period of four months, it was definitely proven that these basic hottops furnished an increased yield of sound billets 2% greater than wasobtained from ingots poured in a fire clay hot top. An increased yieldof 2% in sound billets reflects a saving of approximately thirty centsper ton of steel.

Preferably, the hot top of this invention comprises a plurality ofsheets or slabs of insulating material that disintegrate in use, so thatthe material falls away from the ingot when the ingot is removed fromthe mold. If any material adheres to the ingot, its composition is suchas not to be detrimental to the ingot or the roll scale. The slabs ofwhich the hot top is formed (preferably four in number) fit against theinterior faces of the ingot mold and are sustained inside the top of themold by suitable means in such a way that a part of each of the slabs isinside the mold, and a part of each of the slabs projects above the topof the mold. The projecting portions of the slabs are held in place andreinforced against the weight of the molten metal poured into the moldby wire, metal bands, or a metal casing that fits around the outside ofthe projecting portions of the slabs, as will hereinafter appear.

The invention is illustrated in the annexed drawings, wherein one of theslabs is shown as well as several means for positioning and maintainingthe slabs in place in the upper end of an ingot mold.

In the drawings- Figure 1 is a top plan view of an ingot mold with a hottop of the present invention positioned in the upper end thereof;

Fig. 2, a transverse vertical sectional view on the line 11-11 of Fig.1;

Fig. 3, a perspective view of a further means for holding the slabs ofthe hot top in place;

Fig. 4, a vertical sectional elevation disclosing a slightly differentform of slab positioning and holding means utilizing sustaining hooksand corner clips;

Fig. 5, a fragmentary view illustrating the use 45 This insolublemagnesia-c be employed) partly removed to expose the slab bo y;

Fig. 7, a face view of a metallic blank from which a modified form ofslab supporting and clamping element is produced;

10 Fig. 8. a perspective view of said element produced from said blank;

Fig. 9, a top plan view of an ingot mold with the slab-formed hot toppositioned and held therein by the utilization of clamps such as shownin Fig. 8;

Fig. 10, a vertical sectional view showing the slab at the left insection. while the slab at the right is in elevation; and

Fig. 11, a perspective view of a portion of the upper part of an ingotmold with two of the slab elements positioned therein and held in placeby clamps of the form shown in Fig. 8.

Each of the slabs employed in producing the hot top of the presentinvention comprises an insulatin material of ht, a reinforcing. ateriner the slab being so ma e as o provi e a perms body of greaterinsulating value than the fire clay and fire brick hot tops. The hot topinsulation keeps the top of the ingot soft and mobile longer than thehot tops now in use and prevents or greatly reduces the formation ofvoids and piping in the ingot.

The following is one example illustrative of the practice of thisinvention in the production of the slabs: A sia containing lime producedby burning a dofomite at a low percentage of impurities is treated withwater to remove enough of the lime to produce an insoluble residue whichon an ignited basis has about the 40 following composition:

. Percent MgO 89 a0 10 203+S10z 1 ntaini sludeis o bonated whereofita'mea comprising the corresponding amounts of ma e ium carbonate andcalcium carbonate.

ui car na es are a e a O in wood h vin s and starch and the aggregate ismed Hi5 water orm a moist pasty mass.

The proportions in which the ingredients are mixed are approximately asfollows:

5 Parts by weight Carbonates 89 Wood shavings 5 Starch 6 Water 20 emixture is pressed into slabs under a pressure of 6 lbs. per squareinch. The slabs are placed in a dryer and dried until the water contentis not in excess of 1%. I have found that the temperature required so toreduce the water content of the slabs varies with different materialsand that the minimum temperatures required range from about200 C. toabout 30 C. The dried slab is a u H a strength to withstand shipping andhandling both in storage and in use. I

5 if Wood shavings and other combustible fibrous materials are used asthe reinforcing const'tuent, as in the preceding example. Under-suchconditions it is preferable to'use-a reinforcing constituent that is notaffected by the drying temperature. Certain inorganic andnon-combustible fibrous and ma ma r1 no as s e mild steel Ea areunaffected by the ffi'g'fiest mg temperatures required and retain theiroriginal strength during the drying process, and at the same time do notintroduce any constituents that would contaminate or be deleteriouseither to the ingots or to the roll scale.

The following is one example of the practice of this invention in theproduction of the slabs, wherein the reinforcing constituent is steelmgland the binder is Portland cement. The basic carbonate constituen 1sprep a slurry'b'fi: taining about 17 to 20% of solids by mixing thatconstituent with water. To 76 to 88 parts by weight of this slurry areadded 4 parts by weight of high early strength Portland cement, and 1part by weight of steel wool, and the ingredients mixed to thoroughlydistribute them. This mixture is run into molds and sufhcient waterremoved, either by squeezing it out under pressure or sucking it outunder partial vacuum, to convert it to a thick paste. The material inthe molds is then subjected to av pressure of about 400 to 450 poundsper square inch to produce a slab that can be removed from the molds.These slabs are dried to reduce their water content to less than 1% inthe manner described in the preceding example.

The composition of the dried slabs is approximately:

Per cent Basic carbonates 75 Steel wool u 5 Portland cement 20 The slabswill be made of such size as to conform to the usual measurement of theingot molds. Generally stated, two sizes of slabs are. made, one 23x15x1and the other 17x15xl the smaller slabs weighing about '7 lbs. each, andthose of the larger size about 8 lbs. The slabs necessary to produce thehot top have an aggregate weight of approximately 35 lbs., as comparedto a weight of approximately 200 lbs. and more of the commercial hottops of today. The actual weight of the slabs will, of course, vary withvariations in porosity and is dependent upon the composition of theslab. The preceding weights are cited by way of illustration and not byway of limitation. The slabs may be stacked and closely packed, both inshipment and in storage, and take up about only one-fifth the spacerequired to store an equivalent number of fire clay hot tops.

As above noted, various means may be employed to maintain the slabs inposition in the upper end of the ingot mold. Referring to Figs. 1 and 2,l0 denotes the ingot mold or the upper portion thereof, and II denotesthe various slabs positioned and maintained within the upper portion ormouth of the mold. In these two figures, hooks 12 are employed, theupper ends of which overlie and embrace the upper edge of the ingotmold, while the lower ends are also hook-shaped and extend under andslightly upward of the lower portion or edge of the slabs ll. As will beseen more particularly upon reference to Fig. 2, the upper portions ofthe slabs extend upwardly beyond the upper edge of the mold andlikewise- UI'USS HBTBTBHCG extend a somewhat greater distance inwardlyof the mold. as shown in Fig. 1, one end of each of the slabs isslightly rounded or contoured to fit the filleted comer of the ingotmold, while the opposite end of the slab is straight and takes againstthe inner face of the adjacent slab.

"Thus, the slabs are in a sense interlocked and inasmuch as they aremade to size or approximately so, they may be readily positioned withinthe mold and held in place through the assistance of the sustaininghooks.

In 3, the, upper ends of the slabs which project beyond the ingot moldare embraced by a metallic frame comprising a plurality of plates l3.each end of each plate being out-turned at an angle of approximately 45degrees to its body, so that adjacent ends of adjacent plates stand inparallelism and are provided with openings through which bolts or screwsH may be passed to hold the parts in their assembled position.

In Rigs. 4 and 5, astill further modification is shown, wherein hooks[2, similar to the hooks shown in Figs. 1 and 2 and so lettered, areemployed. Placed at each of the corners of the upwardly projectingportions of the slabs II is what maybe termed a clip, designated by [5,produced from sheet metal bent upon itself at right angles and fittingagainst the adjacent ends of the various slabs. These clips are held inposition by a wire 16 passed about the assembly and twisted at its ends.

A slab is shown in perspective in Fig. 6. As seen in that view, the slabis provided with a covering 11 of relatively impervious paper or likematerial which to a certain degree acts as a reinforcing element and hasthe additional advantage of protecting the slab against the absorptionof moisture. This covering will burn away immediately the molten metalcontacts the same and, therefore, does not militat against the porosityof the slabs. This is a feature of some importance. It will beappreciated that by reason of the nature of the formation of the slabs,they may be trimmed if need be, to secure proper positioning thereofwithin the ingot mold.

In Figs. '7 to 11, inclusive, 9. further modified form of slabsupporting and clamping means is illustrated. As will be seen uponreferenc to Fig. '7, the blank when out out takes substantially the formof the letter H, with the body portion 20 above the cross-bar orconnecting element 2| left integral therewith. Th blank may be said tocomprise a body 20, the base of which is the full width of the blankwith two depending legs-or elements 22 and 28 and two upstanding armsorelements 21 and 25, formed by slitting the blank vertically. The body 20is bent at right angles upon a medial line, while the legs 22 and 23 attheir lower ends are bent inwardly and thence upwardly to produce books26 and 21. The arms 2! and 25 are bent outwardly at right angles, asbest indicated in Fig. 8, and thence downwardly, producing hook-shapedelements 28 and 29. When positioned within the top of the ingot mold andin proper relation to the slabs, the arms'24 and 25 overlie the upperedge of the ingot mold, while the body 20 embraces the adjacent faces ofthe slab elements.

The slabs are supported by the hooks 26 and 21 formed upon the lowerends of the leg elements 22 and 23', so that the'slabs are precludedfrom dropping downwardly into the ingot mold. When the clamps or clipsare mounted at each corner of'themold and'inengagement therewith andwith the slabs as just indicated, the slabs will be quite firmly held inplace, the body 20 embracing the corners and the arms and hooks holdingthe slabs against movement both vertically and laterally.

If desired, a wire 29 may be passed around the upper portion of theassembled slabs or hot top elements and the body 20 of the clips, asshown in Figs. 9 and 11, the wire being twisted to draw the parts intoclose relationship.

By making the parts integral and having the body portion 20 contact theabutting and adjacent slabs, a stable positioning of the parts isensured and facility of placement is simplified over the formspreviously set forth.

From the foregoing, it will be seen that the clamps or clips may beformed from a single piece of metal by a simple operation of slitting orcutting, and then bending the parts to position. They may be said tocomprise a body portion adapted to embrace the adjacent corners or edgesof the two slabs, plus hooks to engage the lower edges of the adjacentslabs and supporting arms which overlie the upper marginal end of theingot mold.

The use of clips or holders of the type just set forth facilitates thepositioning of the slabs with reference to the ingot mold and requiresthe use of only four clips, whereas in the form shown in Figs. 1 and 2eight are required, and in the form of Fig. 4 twelve are needed.Moreover this form greatly reduces the time and labor required inpositioning the insulating slabs to form the hot top.

Any suitable supporting and positioning means may be employed, althoughin actual practice it has been demonstrated that the style of holderillustrated in Figs. '7 to 11, inclusive, is far superior to any othertype of holder so far devised.

The insulating material which comprises the dominant constituent of theslab may be magnesium carbonate, calcium carbonate, a mixture ofmagnesium and calcium carbonates in any desired proportions, or anyother suitable inert insulating material that will not react with themetal being cast. It is essential that the slabs have adequate strengthto permit handling and placement of the same but, on the other hand,they should be so produced that they will disintegrate when subjected tothe heat of the molten metal, and that the constituents of which theslab is produced will not be detrimental to the ingot or the roll scale.

The reinforcing material used to hold the slab constituents together andto afford sufiicient strength and a certain degree of flexibility, maybe wood shavings, excelsior, cellulose fibre or any other fibrous andmatted organic or combustible substance, or it may be steel wool, steelshavings or any other fibrous or matted inorganic substance which isfree of ingredients that would be detrimental to the ingots or the rollscale.

The reinforcing of the slab need not be imparted entirely or even inpart by an interior matted fibrous substance, but may be appliedexteriorly to the surface of the slab, provided it be of such a natureas not to interfere with the disintegration of the slab when it isheated in contact with the ingot. Exteriorly applied reinforcingcovering the faces of the slab has the additional advantage ofprotecting the slab from the absorption of moisture, and thereby reducesthe tendency to boil.

The cementitious material or bond may be starch, glue, sodium silicateSorel cement, gyp- SUIII, Portland cement 01 any OEHG! cementing mediumthat will serve to form a consolidated slab. Preferably, the bindershould have the property of disintegrating when subjected to the heat ofthe molten metal within the time that the ingot remains in the mold.

After the hot top is formed by placement of the slabs in the upper endof the ingot mold, the molten metal is poured through the hot top andpasses down into the mold. when the insulating constituent of the slabis composed of carbonates of magnesia and lime in substantially theproportions above specified, the heat of the molten metal will transformthe carbonates into oxides that are highly refractory and prevent thetransmission or dissipation of heat therethrough. It follows, therefore,that the top of the metal of the charge remains molten for aconsiderable period of time and much longer than with the hot tops nowin commercial use. In a specific case, the surface remained molten fortyminutes when hot tops of the present invention were used, and onlytwenty-nine minutes when fire clay hot tops were employed, and theaverage sinkage of the top of the metal was 5 inches with the new hottop as compared with 3.7 inches with the clay top. indicating thefilling of more voids in the ingot when using the new top. Theprolongation of the freezing time of the top of the ingot may be greateror less than in this case, depending on the insulating qualities of theslabs and on other variable conditions. In any event, due to thesuperior insulating qualities of these slabs, the freezing of the top ofthe ingot is delayed long enough to allow more time for the molten metalat the top to sink in the mold as the ingot shrinks, and fill the spacethat would otherwise develop as pipes and voids. Due to the heat of themolten metal, the slab disintegrates in about 15 to 20 minutes, withoutreacting with the metal.

It is recognized that the time required for the disintegration of theslab varies, depending on the thickness, the density and the compositionof the slab. However, when the ingot is removed from the mold, in aboutan hour, the disintegrated material falls away of itself. If, perchance,any of the material does adhere to the ingot its composition is such asnot to be detrimental to the roll scale. The resulting roll scale is,consequently, uncontaminated by objectionable material derived from thehot top.

The invention is not to be restricted to a particular method of makingthe slabs. They may be made by molding, pressing or extruding, or anyother method which will produce a slab. The pressure used in moldingshould not be great enough to impair the porosity of the slab or to makeit so dense as to render its adequate drying diflicult.

Moreover, the invention is not to be restricted to a particulartemperature or duration of time of drying, Care must be exercised,however, in drying the slabs in order not to impair their strength andmake them brittle. Too rapid drying and drying at too high a temperatureboth have a tendency to make the slabs brittle and result in loss frombreakage. The drying may be carried out in any manner that will producea slab having the requisite strength and that will not boil whensubjected to heat of the molten metal. Both in transportation andstorage the slabs should be protected against moisture, which would tendto cause boiling when in use.

In its broadest aspect this invention pertains to a hot top whichcomprises a consolidated mass of insulating material that disintegrateswhen W. 1W1. .s-e a A subjected to a high temeprature and which is ofsuch composition that it will not contaminate the roll scale withobjectionable matter. Though the invention has been described in termsof a hot top formed from slabs, the application of the invention is notlimited to such slab construction, but includes hot tops consisting of asingle unit and molded forms.

What is claimed is:

1. A hot top for ingot molds, comprising a plurality o earate slabseachmmnusaiinnthe e (1 basic inorgani eat insulating material, an acementitious binding substance for holding the basic material together,said hot top being characterized by the property of disintegrating to apowdery mass of non-adherent particles when subjected to the heat of themolten metal teemed into the mold to produce an ingot.

2. As a new article of manufacture, an insulating slab comprising anadmixture of the following: magnesium and calcium carbonate, a fibroussubstance, and at least one binding substance, said carbonates formingthe major portion of the slab, said slab being characterized whensubjected to the temperature of molten metal by the absence of boilingand the ultimate disintegration of the slab as a whole into non-adherentparticles.

3. A hot top element for ingot molds, comprising 89 parts by weight offinely divided magnesium and calcium carbonates, 5 parts by weight ofwood fibre, and 6 parts by weight of starch, said element beingcharacterized by the property of disintegrating when subjected to theheat of the molten metal teemed into the ingot mold.

4. A hot top for ingot molds, comprising in the main a basic inorganicinsulating material combined with a reinforcing material and 9.ccmentitious binder, said hot top having the property of disintegratingwhen subjected to the heat emanating from the metal teemed into the moldto produce an ingot.

5. A hot top for ingot molds, comprising in the main at least one basiccarbonate combined with a relatively small amount of steel wool as areinforcing material and a cementitious binder, said hot top having theproperty of disintegrating when subjected to the heat emanating from themetal teemed into the mold to produce an ingot.

6. A slab for use in the formation of a hot top for ingot molds, saidslab comprising predominant amounts of the carbonates of magnesium andof calcium, a relatively small amount of fibrous strengtheningmaterial,v and a binding material likewise present in a relatively smallamount, said slab being characterized by being porous, light in weight,and having the property of disintegrating to a powdery mass ofnon-adherent particles under heat from the molten metal.

7. A slab for use in the formation of a hot top for ingot molds, saidslab comprising predominant amounts of finely divided carbonates ofmagnesium and of calcium, a relatively small amount of combustiblefibrous strengthening material, and a relatively small amount of starchserving to bind the various carbonate elements together when subjectedto light pressure, said slab being characterized by being porous, lightin weight, and having the property of disintegrating to an amorphousmass of non-adherent particles under heat.

8. A slab for use in the formation of a hot top for ingot molds, saidslab comprising predominant amounts of finely divided carbonates ofmagnesium and of calcium, a relatively small amount of steel wool, and arelatively small amount of Portland cement serving to bind the variouscarbonate elements together when subjected to pressure, said slab beingcharacterized by being porous, light in weight, and having the propertyof disintegrating to an amorphous mass of non-adherent particles underheat.

9. A hot top element, comprising parts by weight of finely dividedmagnesium and calcium carbonates, 5 parts by weight of steel wool, 20parts by weight of Portland cement, and water, said ingredients beingadmixed, molded, and dried, said element being characterized by theproperty of disintegrating when subjected to the heat of the moltenmetal introduced into the mold.

ISAAC A. NICHOLAS.

